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Solving mysterious corrosion in a pressure vessel

A leading global manufacturer of chemicals faced a significant corrosion problem in some of its metal tanks. The tanks contained the final product of a peracetic acid production line: an equilibrium solution that included fractions of acetic acid, hydrogen peroxide, a stabilizer, a catalyst (mineral acid) and peracetic acid.

A few months after the tanks were installed, the team realized they were corroding very quickly — but only in areas where the tank was exposed to vapor. No corrosion showed where the tank held liquid. Failure to address the corrosion would create significant safety hazards. A cracked tank could result in a dangerous spill of caustic materials and release hazardous vapor into the environment.

The engineering team began running highly targeted searches on Knovel to access results vetted by experts and tailored for engineers. With the help of the data a process engineer found in Knovel, she was able to understand the unusual interaction of the equilibrium solution with the tank and pinpoint the root cause of the corrosion: an unexpectedly high temperature was raising the pressure in the tanks. That resulted in the formation of acetic acid vapors that accelerated corrosion of the steel under those operating conditions. To address the acidic vapor issue, the engineering team made a change to the storage process.

Resolving the corrosion issue not only improved the safety of the company’s operation but also made it easy to maintain the quality of the final product — and preserve the company’s reputation. The product costs up to $1.25 per liter to manufacture, so with three tanks containing more than $50,000 of product apiece, each batch costs more than $150,000 to produce. Thanks to Knovel, the R&D executive and his engineering team were able to quickly find a solution to steer clear of a number of potentially devastating outcomes.